Prestressed beams

Abstract

After a historical note about the origin of prestressing and its expected effects on RC elements, this chapter presents the main features of the two technologies, one based on the pretensioning and the other on the postensioning of the steel tendons, including the effects of prestressing losses. A discourse on the tendon profile in the beams is developed to orientate the deign choices. The resistance calculations of the current prestressed sections are eventually presented, concluding with the specific analysis of tendons anchorage and stresses diffusion. In the final section three calculation examples are shown related one to a precast pretensioned floor element, one to a precast post-tensioned beam and the last one to a flanged beam provided with a cast-in situ upper slab.